Polyester resins, both branched and linear, are used in various heat-sealable adhesive and protective coating applications. Some of these applications require that the resins be dissolved or diluted with a solvent. The low molecular weight polyesters are readily soluble in common organic solvents. The high molecular weight and partially crystalline polyesters are not easily soluble. It has been disclosed in U.S. Pat. Nos. 4,419,476, 4,298,724, 4,581,093, 4,486,508, and 4,487,909 that if high molecular weight polyesters are branched they can be made soluble in inexpensive, relatively nontoxic organic solvents. It is the linear polyesters, however, that impart improved chemical and heat resistance to the adhesives and coatings in which they are used, and these linear, crystalline polyesters are not soluble in the same relatively nontoxic solvents.
Currently, the high molecular weight, linear polyesters are most commonly dissolved in dioxane and chlorinated solvents. Dioxane emits formaldehyde, a suspect carcinogen, and halogenated compounds are also considered suspect carcinogens, which makes their use as solvents environmentally questionable and potentially dangerous to health. Attempts to find innocuous substitutes have been hindered by marginal solubility of the linear polyester resins in the less toxic solvents, or by solvent evaporation rates that are either too fast or too slow to be functional in coating applications. Thus, there exists a need for solutions of high molecular weight, linear, partially crystalline polyesters in a solvent formulation that is low in toxicity, and consequently without the disadvantageous environmental and health related effects of the organic solvents commonly used for those polyester resins.